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We take it for granted
that this year's model is better, whether it is a personal car,
a pickup truck, or the equipment we use in our business. Most of
the latest models in construction equipment do perform better, but
the reasons are not always confined to the obvious changes. New
techniques–a whole new approach to the type of equipment used–are
making the work not only more productive but more comfortable too.
Scrapers used to be the machines on which inexperienced workers
would start (and make all their mistakes) because they were perceived
in much the same way as the old family car for the teenager with
the new license. Spending some time training operators to run equipment
efficiently will soon pay for itself in better work, believe owners
of scrapers and graders.
Comfort in a rumbling,
ground-grabbing machine such as a scraper does not mean that the
operator sits back and lets his equipment do all the work and make
all the decisions, but it does mean that he or she will not be tired
by lunchtime and unproductive in the afternoon. Comfort, when we
are talking about excavation and grading machines, has nothing to
do with laziness. Quite the opposite is true. The comfortable operator
works well for more hours, and usually the work is more accurate.
The ability of the operator to concentrate on the assigned job (rather
than on aches and awkward sitting positions) has great influence
on getting that job done right the first time.
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| This
tire was developed especially for large scrapers. |
Scrapers–considered
ideal machines for earthmoving jobs involving short distances, less
than a mile, say–usually work on rough, unfriendly terrain.
What makes the contact between a scraper and the ground it works?
The tires. Which parts of a scraper can stop the machine if they
malfunction? The tires. We can become so wrapped up in cubic yards
of capacity and horsepower that we ignore those components of scrapers
and graders. They might be so obvious that we don't notice them.
"They could be the parts you change most often," observes
Keith Mitchell, whose contracting company has worked scrapers in
the Dakotas, Wyoming, and Montana. "It helps my costs if the
tires last a long time." The larger the ground-contact patch
for scraper tires, the more likely they are to enjoy long life,
and there are other aspects of tire design that can contribute toward
better operator control and comfort. Michelin introduced a radial
tire especially for large scrapers. The XMS is described as an E3
tire, available in 40.5/75 R39. Its practical goal is to provide
the scraper user with good traction, superior resistance to damage,
and a smooth ride.
It has been our experience
that, anytime a tire manufacturer develops a tire specifically for
one type of construction machine, the product is worth serious consideration.
We have seen it with skid-steers, wheel loaders, and now scrapers.
"It has a high lug-to-void ratio," states the manufacturer,
accounting for claims of better performance. "The staggered
tread blocks help improve operator comfort, while the edges of the
tread pattern offer exceptional lateral grip." The tread on
this Michelin tire has a square format to protect the shoulders
and sidewalls, and there is a thick rubber bridge at the base of
the tread, designed to increase the strength of the tread blocks
and create strong resistance to punctures.
So much for the specs.
What does a user say? Dave Coveney of Ford Construction in Lodi,
CA, tells us that his 31 scrapers come across many different soil
conditions. "We needed a tire to cope with all those
conditions, and the XMS has proven its superiority over some other
well-known brands. We are getting more than 3,500 hours off the
front tires, and the Michelins have been about 20% better than any
others we've tried. Sometimes our scrapers are traveling at
more than 30 miles per hour, and the tires must be able to handle
that."
You'll find phrases
such as "enhanced productivity and operator comfort" in
most manufacturers' scraper brochures. The reason is that those
two features have been requested by users. With large construction
machines, manufacturers will not change the design every year because
the cost is prohibitive. The G Series of scrapers from Caterpillar
started arriving in 2000; nobody should expect an H Series this
year. Among the new features that make the G Series better than
its predecessor (the F Series) are improvements in the power train
(with an electronically controlled tractor engine) and in the controls
(with a single joystick replacing three implement control levers).
Filling the Scraper
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| Agricultural
tractors are finding plenty of work at construction sites. |
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| Self-contained
scrapers have a history of productive success. |
The two most popular
techniques for filling a scraper have been a push-load system and
one that is self-contained and independent. The Cat 627G is a good
example of the latter. With a capacity of 20 yd._, plus twin engines,
it can load independently or be push-loaded. The auger-scraper arrangement
for this model gives it a self-loading capability and expands the
capacity to 21 yd._, while the push-pull configuration has the machine
working in tandem with another 627 to give high production and low
cost per yard. G Series scrapers from Caterpillar have been designed
to give the lowest cost per yard for road construction projects
and site development where the amount of material to be moved is
less than 500,000 yd._ The manufacturer expects this type of scraper
to be used when the hauling distance is more than 1,000 ft. Cat
D8 and D9 tractors have worked well with both the 621G and 627G.
"The biggest advantage
is that self-contained scrapers really do self-load," asserts
Dennis O'Rourke, owner of Sureway Construction in Alberta, Canada.
He is talking about auger scrapers, Cat models with tandem power:
an engine for the tractor and another for the scraper. "They
are cutting ditches, building highways, and stripping ahead,"
adds Joel Yundt, project superintendent for the contractor. "They
have an auger, so you can mix material while you're loading, which
makes the fill easier to manage. We don't have to dedicate a grader
or dozer to work in the fill."
The TS14G from Terex
is the heir to more than 11,000 TS14 scrapers in previous series
(B, C, D, and F) that have been working worldwide. It is recommended
by the manufacturer for small to medium earthmoving projects. The
340-hp machine has a heaped capacity of 20 yd._, a struck capacity
of 14 yd._, and a payload of 48,000 lb. Among the benefits offered
by this scraper, Terex stresses the low maintenance costs, helped
by the new, extended intervals for oil changes (450 hours with the
manufacturer's filters), fuel filters (900 hours), and coolant filters
(also 900 hours). Maneuverability of the scraper is important to
the operator, and efficiency in this aspect of the machine's operation
can significantly improve the daily productivity. The TS14G can
complete a full turn within a width of 33 ft. It has full 90°
steering to the right or left, with two hydraulic cylinders (mounted
low to improve stability) providing the power. The degree of rotation
of the steering wheel controls the speed of the turn.
Some of the discomfort
in yesterday's scrapers was caused by the working motions of
the scraper's bowl. Terex offers a cushioned bowl suspension
system, especially appreciated at higher speeds. To attain good
penetration of the ground, the bowl uses positive downpressure while
the semiradial, power-down apron gets down and around the load smoothly.
Recognizing that all "earth" is not the same, there are
reversible, interchangeable, four-piece cutting edges that can be
adjusted in drop center or alternative configurations. What seems
a small point, but might be most practical, is that the arms of
the apron are mounted outside the bowl, so they are neither
impacted by the abrasion of the load nor restricted by it.
The Third Option Continues
to Win Support
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| Longer
service intervals for scrapers reduce operating costs. |
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| Scrapers
often work in tandem for greater productivity. |
There is a third method
of loading: the tow-along (or pull-type) scrapers. These are really
attachments, and they originated in the farm machinery sector. They
are pulled by agricultural tractors, and some companies making them
have been successful since the beginning of the last century. There
seems to be a continuing revival of interest in these types of scrapers
for construction-related projects, and some people in the industry
have forecast that they will eventually take over from independent
or self-contained scrapers as the preferred equipment. Miskin Scraper
Works, for example, has been making dirtmoving equipment since 1917.
It has introduced scrapers for construction use (with 9-, 17-, and
24-yd. capacities) that can be pulled as single units or in a train
of scrapers behind a single tractor. These construction scrapers
are heavier and built more ruggedly than their agricultural relatives.
"The 24-yard model is the biggest scraper capacity anywhere,"
says Mike McRory for Miskin in Mississippi. "Road builders
like our scrapers. One reason is that there is nothing to go wrong
on them–no transmission, for example. They work and work, and
the user may well change his tractor before he has to change the
scraper." The tow-along scraper is a simple, tough, and reliable
piece of equipment, which explains why grading and excavating contractors
are finding it so interesting.
Currently the largest
manufacturer of tow-along scrapers, Reynolds International in McAllen,
TX, reminds us that these earthmoving machines can be pulled by
either track-type or wheeled tractors–whichever is available
or better for the terrain. Reynolds calls its scrapers the Carry-All
range and describes them as having a basic design that involves
a front gate and pivoting bucket. We counted 17 models (including
some with low ground pressure for the most sensitive terrain) with
heaped capacities from 5 to 18 yd._ and cutting widths up to 168
in. While the larger models require tractors with 300 hp or more
for a single-unit system, the small ones can be worked by 100 hp
or less. A recent model, the 17E10.5, is described as an ejector
scraper with laser leveling. It has a three-piece, reversible cutting
blade to fill the 17-yd._ bowl. How much does it cost to run a tow-along
scraper as opposed to a self-contained unit? Reynolds has a spreadsheet
available for calculation of those costs, based on the initial investment,
repair costs, distance to be covered, speed required, efficiency
of the system, and swell factor.
Some parts of our country
had a dry summer this past summer. In South Carolina, pond levels
were low or nonexistent. "This has meant that landowners have
been able to clean out their ponds for the first time for years,"
observes Brian Derrick of Ridge Spring, SC. "They have used
tow-along scrapers to do it." In Alabama, tow-along scrapers
have been used for similar work. "We use them here to build
pond dams," says Dane Linton of Goshen, AL. "They require
no maintenance, and the ones we favor [Prime Manufacturing] are
well built." Another popular site for a small tow-along scraper–a
7-yd.-capacity model, for example–is ground being prepared
for building foundations.
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| These
tow-along scrapers are simple, rugged pieces of equipment. |
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Prime Manufacturing in
Poplarville, MS, is an old-time company. "Our scrapers–some
of them also known as Carry-Alls–are recommended for a variety
of jobs, including general land management, building ponds and roads,
and the preparation of construction sites," comments Payton
Morrison of Prime. "Pull scrapers are generally not recommended
for excessively rough, moist, or rocky conditions that require push
assistance from a bulldozer or do not permit all of the scraper
tires to remain in contact with the ground." Morrison adds
that pull-type (or tow-along) scrapers are appropriate for jobs
that require the movement of less than 500,000 yd. of dirt. That
amount seems to be the minimum required to provide significant profit
for self-contained scrapers. Because the regular maintenance of
a pull scraper will prolong its life, Prime recommends regular inspection
of hydraulic lines and connections for leaks or damage, as well
as a daily application of grease to all grease fittings and inspection
of tire inflation, tongue and lug bolts, hubs, wheels, spindles,
blades, and all pin connectors.
The consensus among contractors
seems to be that a tow-along or pull-type scraper is less expensive
than a self-contained unit. Users can purchase a power unit, such
as a tractor, that will perform multiple tasks by using different
attachments, and the wear on the scraper is significantly less costly
than that of a self-contained unit. It can also be easier to transport
a tractor/pan combination. Reports also indicate that the tow-along
scraper is easier to trade in or resell, a point that is especially
useful for those contractors who might need scraping equipment for
only occasional projects. But again, tow-along scrapers are not
recommended for soils that include large rocks, and hard or frozen
soils might require special bits or ripping first.
Other companies offering
tow-along scraper systems include John Deere and New Holland, both
leaders in the manufacture of agricultural tractors. "A key
reason for the success of pull-along scrapers has been the improvement
in tractors," notes Randy Rust of Ashland Industries in Ashland,
WI. "Grading and excavation contractors are accepting that
these powerful tractors–some of them with nearly 500 horsepower–can
play an important role in construction as well as in their original
market, agriculture. Some of today's drawbar configurations
transfer much of the weight to the power unit, and the flotation
you can get with a tractor-plus-scraper combination means you can
extend your working season to include those times at the beginning
or end of the regular season when self-contained scrapers may not
handle the wet or muddy ground." With a well-designed transfer
of weight, the same gross weight can handle a larger capacity. Ashland
tow-along scrapers tend to be "narrow and stout" rather
than wide; that might help them deal with a wider variety of soils,
including clay dirt and tight clay. To put it simply, a narrow scraper
lets the tractor pull more easily and deeper.
Just Fine, Thank You!
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| Grader
manufacturers pay special attention to blade design and control |
It amazes most people
that a grader can be so accurate. I've met people who wonder how
a "big, awkward" grader manages to go straight when it
has that big blade always at an angle. Whatever the public perception,
the motor grader has been one of the most frequently used machines
for both public and private applications. Contractors agree that
being able to see where the blade is going is a prime consideration
in selecting a grader, but there is still plenty of operator skill
and concentration required to make sure the work is done in as few
passes as possible. Years ago, some contractors told us, the new
workers would learn on the scraper and end up on the grader. The
chief skill required of a grader (or scraper) operator is the ability
to steer in the right direction, regardless of the bumps and slopes.
Scraper drivers soon learn whether it is better to turn going down
the slope or up. A feature on Komatsu's Laterra graders is the circular
geometry blade. It enables 90º bank sloping and accurate positioning
while giving good ground clearance. There are three models in the
Laterra series, with operating weights from 30,525 to 34,390 lb.
The horsepower varies from 140 to 180, and variable horsepower is
available on all models.
Fine grading is
a term still used. It seems almost unnecessary to say it now, because
graders are so accurate as they level the ground, whether it is
for a new road, reshaping an old road, or for basic grading work
at construction sites. One of the challenges for traditional self-contained
graders comes from equipment such as skid-steer loaders that can
do the fine grading for contractors if the right attachments are
mounted. It would be a mistake, however, to imagine that a small
loader will be more accurate (i.e., give a smoother result) than
a self-contained motor grader.
The design and use of
the blade seems to control success. Volvo says its graders (the
ones we used to know as Champions) in Series VI have blades that
are right for every job. The operator can set the blade angle up
to 90º vertically on both sides of the machine, as well as
adjust a 21º down angle for clearing and cutting ditches. The
mobility of the blade allows the operator to clean ditches in a
single pass while keeping the grader's wheels up on the shoulder
where the traction is usually better. Volvo also claims that the
Series VI blade has the longest reach outside the tire profile to
improve cycle times and enable the user to cut a 2:1 bank slope
with the moldboard completely outside the tire profile. The operator
can also lower the blade to some 33 in. for a deep cut, while the
lift above ground means that the blade can be carried over obstacles
at the job site.
All-wheel drive for a
grader has obvious advantages. This kind of system distributes the
power evenly to each front wheel and, if traction changes at either
front wheel, gives instant power adjustment so that the best pulling
power is attained. The system can be used in two-, four-, or six-wheel
modes. When the all-wheel drive is disengaged, the grader will return
to four-wheel tandem drive with no parasitic loss. Also consider
the possibilities of the Champion Creep Mode. This lets the operator
disengage the rear drive and pull the grader at low precision-grading
speeds, using only the hydrostatic front-wheel drive.
Do you use your grader
for roadwork? This is usually a municipal or county job, but the
trend toward outsourcing or privatization for some public works
makes one wonder if grading contractors could capture worthwhile
contracts in that sector. There are many thousands of miles of gravel
roads; they enjoy grading at least once a year. An attachment we
spotted that seems worth investigating for grading where there are
ditches is the Road King Sloper from Rockland Manufacturing in Bedford,
PA. "It can double your grader's productivity," claims
Bob Shaffer for Rockland. "You can use this sloper and articulate
the grader at the same time, while the extra reach to the side means
that the grader stays on the road and out of the ditch. It can also
be used for tail grading if you get that attachment too."
Frequent contributor
Paul Hull writes on construction and environmental topics for several
international magazines.
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